Students design device to monitor fetal oxygen levels

Rice University students have created a prototype device to monitor the pulse and oxygen levels of a fetus undergoing endoscopic surgery in a mother’s womb. The WombOx team of senior engineering students collaborated with the Texas Children’s Fetal Center to create the device, which miniaturizes the components found in a pulse oximeter commonly clipped to a patient’s finger.

Pulse oximeters read oxygen levels in the blood by comparing light from a source to the light that reaches a detector on the other side of the finger, and can calculate oxygen saturation by sensing how much light is absorbed by the tissue. This kind of information has not been available to doctors working to help fetuses suffering from congenital defects such as spina bifida, and Texas Children’s Hospital is pioneering efforts to treat such conditions through the endoscopic procedure known as fetoscopic surgery.

During surgery, doctors monitor the health of a fetus through ultrasound, but that only gives them a heartbeat. Knowing oxygen levels in the blood is critical when doctors need to act quickly to help a fetus in distress, and the WombOx device offers potential for providing this data in real time.

The bioengineering students, Claudia Iriondo, Thomas Loughlin, Samir Saidi, and Kathryn Wallace, worked closely with Dr. Magdalena Sanz Cortes, an associate professor of obstetrics and gynecology at Baylor College of Medicine and a clinician at the Texas Children’s Pavilion for Women; and Eric Richardson, the student’s Rice faculty adviser and engineering lecturer. The prototype is the product of the students’ capstone design project, required of most senior engineering students at Rice. The team won the top Willy Revolution Award, a $5,000 prize presented at Rice’s annual Engineering Design Showcase for innovation in design.

“This project was challenging because of the size of the instruments that we work with,” says Sanz Cortes. “When we started talking about the whole project, we talked about the size of a pulse oximeter. Transforming that into the size of the device they have created is very challenging.”

The device consists of a loop of wire on a hollow stick, where the wire is a special hybrid that expands to a predetermined shape at the correct temperature. It carries LEDs and a photodetector on miniature circuit boards that illuminate and sense the flow of blood through the tissue underneath. The loop is packaged in a retractable sheath that fits through the small incision made in fetoscopic surgeries. The tube is inserted into the mother’s womb and the loop is extended, and once it expands, doctors can use the camera’s video feed to guide the loop around a limb and tighten it, putting the sensors in place to monitor the fetus throughout the procedure.

The team tested their device at the Oshman Engineering Design Kitchen on a baby doll in a ball, inserting a rudimentary WombOx through a port that models an incision and successfully looping it around the arm of the doll within, following their progress on a monitor. The device will now go to engineers at Texas Children’s for further refinement and validation.

“A lot of doctors have encouraged us and said, ‘This is amazing, I’m glad you guys are doing this.’ No one is talking it up because there’s not a huge return on investment, but this will be amazing if it can actually monitor a fetus’s vital signs and intervene if something goes wrong,” says Wallace.

Texas Children’s Fetal Center

women.texaschildrens.org/fetalcenter

Rice University

www.rice.edu